Clinical researchers and basic scientists at the Children's Hospital of Philadelphia and on the campus of the University of Pennsylvania, including the Hospital of the University of Pennsylvania and the University of Pennsylvania School of Medicine, as well as those at nearby institutions, are increasingly engaged in research projects that require the use of highly sophisticated flow cytometry and cell sorting instrumentation. This technology is particularly critical to the success of many funded projects engaged in by investigators from the University of Pennsylvania Cancer Center and the Center for AIDS Research. For those investigators, working with potentially pathogenic materials, such as HIV, hepatitis, herpes simplex, among others, access to flow cytometry and cell sorting for live, unfixed material is not currently available in the Philadelphia area. Because of the potentially biohazardous nature of these agents, it is not possible to perform studies of cells containing live agents in a conventional flow cytometry facility. This represents a serious limitation for those investigators engaged in research on cell function. The BSL3 Flow Cytometry and Cell Sorting Facility will build on the currently successful centralized flow cytometry services available on the University of Pennsylvania campus to provide diverse, technically sophisticated cell sorting and analysis services for those investigators working with potentially biohazardous materials. These services are critical to understanding the basic processes of cell activation and differentiation as well as to finding the translational relevance of such processes to multiple conditions such as AIDS, tuberculosis, hepatitis, and the neoplastic condition. As a centralized resource, the BSL3 facility will not only provide instrumentation and services in a cost-effect manner, but will work closely with investigators on experimental design, data analysis and data interpretation. Based on the highly successful experience of the University of Pennsylvania Cancer Center Flow Cytometry Facility, it is expected that this close relationship will stimulate new applications by researchers and facilitate interactions among investigators involved in research. The range of user research interests is reflected in the diversity of projects presented below. This diversity of user needs necessitates the maintenance of a highly versatile, state-of-the-art BSL3 flow cytometry facility staffed by scientists and technicians with recognized expertise. The Cytomation MoFlo Ultra-High Speed Flow Cytometer provides an optimal platform for sorting in a BSL-3 setting.